One field of application for the invention is holding together a bone and a support member in a desired relative position, while allowing in some cases a limited amount of relative movement, for example to aid in healing of breaks or to correct bony structure deficiencies and abnormalities. In particular, sufferers of abnormal spine curvature or other spine deficiencies may benefit from the invention.
The spine is formed of superposed vertebrae, normally aligned along a vertebral axis, from the lumbar vertebrae to the cervical vertebrae, each having an anterior part: the vertebral body, and a posterior part: the vertebral arch (or neural arch), the anterior and posterior part enclosing the vertebral foramen. Each vertebral arch is formed by a pair of pedicles and a pair of laminae, with transverse processes and/or a spinous process (or neural spine) projecting therefrom. The transverse processes and the spinous process project opposite to the vertebral foramen.
When the vertebrae are articulated with each other, the vertebral bodies form a strong pillar for the support of the head and trunk. In between every pair of vertebral bodies, there is an intervertebral disc.
When the spine of a person has abnormal curvature (e.g. scoliosis) or other deficiencies (e.g. a damaged intervertebral disc), the vertebrae are typically too close together, too far apart or otherwise misaligned, and there is a need to stabilize the vertebrae in a correct position relative to one another. Mainly, there is either a need to compress the vertebrae (i.e. to bring and hold them closer together) or a need to distract the vertebrae (i.e. to move and keep them away from each other).
Devices known in the art for holding vertebrae relative to one another typically include one or more rods that are held by devices attached to the vertebrae by means of screws, hooks, or flexible ligatures. One such device is described in patent document EP2052689A1. This known device comprises a holding body having a receiving portion for receiving the rod and an engagement portion, a closure member for engagement with the engagement portion of the holding body to secure the rod within said receiving portion, and an anchor member for anchoring the holding body to the bony structure of a vertebra.
In the device of EP2052689A1, to create a connection, the receiving portion of the holding body has to be sized to the gauge of the rod used. Since, depending on the specific intervention and patient, a variety of different rod gauges may be required, different holding bodies adapted to accommodate each specific rod gauge need to be provided.
While known devices have proven effective, further improvements would be beneficial.